This application claims the priority of German patent document 100 52 304.8, filed Oct. 20, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method and apparatus for digitally measuring the frequency of high-frequency, pulse-type and low-frequency signals, by an integration of the signal phase.
Currently known systems and methods for measuring the frequency of high-frequency signals are based mainly on IFM frequency measurement and frequency measurement by means of a counter. IFM Instantaneous Frequency Measurement frequency measurement requires a high-expenditure analog analysis and compensation of the temperature drift of the delay elements and of the HF High Frequency component. Frequency measurement by means of a counter is based on the time measurement between zero crossings of the signal, which results in a difficult analysis in the case of very low-frequency as well as very high-frequency signals.
It is therefore an object of the present invention to avoid the above-mentioned disadvantages and to provide a system and a method by means of which the frequency of both low-frequency and high-frequency signals can be measured.
Another object of the present invention is to provide a system and a method by means of which the frequency pulse-type HF signals can also be measured.
These and other objects and advantages are achieved by the present invention, which provides a system for measuring the frequency with an integration of the signal phase. The system includes a phase accumulator by means of which the signal phase of a signal (whose frequency is to be determined) is integrated at predetermined time intervals. A first intermediate memory is controllable for reading a first output value of the phase accumulator after a predetermined first number of time intervals; and is further controllable for reading in a second output value of the phase accumulator after a predetermined second number of time intervals. A second intermediate reads in the first output value of the first buffer register and multiplies it by a first factor which corresponds to the quotient of the second number of time intervals and the first number of time intervals. A subtracter subtracts the first output value multiplied by the first factor from the second output value; and a divider divides the output value of the subtracter by a second factor which has a value corresponding to the first number of time intervals multiplied by the difference of the second number of time intervals and the first number of time intervals. The output value of the divider assumes a value which is proportional to the frequency to be measured.
Furthermore, to achieve the above-mentioned object according to the invention, a method is provided for measuring the frequency with an integration of the signal phase, which comprises the following steps: at predetermined time intervals integrating the signal phase of a signal whose frequency is to be determined; storing in a first intermediate storage the integrated signal phase after a predetermined first number of time intervals for obtaining a first output value; storing in a second intermediate storage the integrated signal phase after a predetermined second number of time intervals for receiving a second output value; multiplying the first output value by a first factor which corresponds to the quotient of the second number of time intervals and the first number of time intervals; subtracting the first output value multiplied by the first factor from the second output value for obtaining a third output value; and dividing the third output value by a second factor which corresponds to the first number of time intervals multiplied by the difference between the second number of time intervals and the first number of time intervals, for obtaining a fourth output value, the fourth output value assuming a value which is proportional to the frequency to be measured.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.